docs(changelog): add changes of tox branch

doc/changelog.rst

@@ -18,13 +18,24 @@ Next Release
 
 - Improvements:
 
+  - add tox integration
+
+    - run tests under Python interpreters 2.7, 3.4, 3.5, 3.6, 3.7
+    - run tests with coverage
+    - build documentation and check links
+    - check sdist
+
+  - optimize setup_requires in setup.py (faster installation)
+  - mark unreliable tests as unstable
+  - define timeouts for all tests
 
 - Bug Fixes:
 
   - :issue_ghe:`678` script validation does not work
   - :issue_ghe:`663` cannot rename connected data port of type object
   - :issue_ghe:`684` ``test_simple_execution_model_and_core_destruct_with_gui`` fails when running core & gui tests in a row
   - installation of fonts under Python 3
+  - various test fixed for Python 3
 
 - Changes: